PROJECT SUMMARY PROJECT SUMMARY The goal of this proposal is to establish a novel gene therapy approach for treating life-long genetic diseases, such as the hemophilias and lysosomal storage disorders, which disproportionally impact children's health and development. We hypothesize that T cells can be engineered to secrete circulating proteins, that these gene- modified T cells will be long-lasting in vivo, and can be used to treat genetic diseases caused by a deficiency or defect in the circulating protein. The rational for this strategy is that (i) gene-modified T cells are being used in the clinic for treating cancer and have passed regulatory hurdles and demonstrated safety in over a decade of use, (ii) T cells have a very long lifespan and gene-modified T cells have been found to last for >10 years in humans, (iii) there has been no immune response against gene-engineered T cells in human, and (iv) there is already major infrastructure to bring this therapy to the clinic. In preliminary studies we have established that (i) human T cells can be engineered to secrete FIX, FVIII and Galc (defective in Fabry Disease), and (ii) transfer of FIX expressing human T cells in to immunodeficient mice results in stable FIX expression, (iii) transfer of FIX expressing mouse T cells in to immunocompetant mice results in stable engraftment and circulating hFIX expression with no anti-FIX immune response. Our Specific Aims will further validate gene-engineered T cells for gene replacement therapy (Aim 1), and improve therapeutic efficacy (Aim 2). In Aim 1, we will evaluate the effectiveness of T cell gene replacement in pre-clinical disease models. These studies will test the hypothesis that injection of gene-modified T cells in to mice deficient in FVIII or FIX will improve the mice?s phenotype. These studies will provide important preclinical data to move our approach to the clinic. In addition, we will also evaluate the use of CRISPR/Cas9 to target integration of a FIX expression cassette in to the CCR5 safe harbor locus of T cells, as a potentially safer alternative to LV-mediated gene transfer to T cells. In Aim 2, we will establish an approach for on-demand expansion of gene-modified T cells in vivo. We hypothesize that vaccination with antigen recognized by gene-modified T cells will expand the T cells and improve therapeutic index. These studies will establish a novel means to improve the efficacy of our approach. This project will establish a new treatment for genetic diseases. The clinical translation of this approach will be greatly facilitated by the massive infrastructure and safety already established for chimeric antigen receptor (CAR) T cell therapy. This makes it possible that upon completion of these studies, this new approach can be moved towards the clinic and ultimately improve patients? lives.